The liquid crystal display device, e.g. a liquid crystal television (TV) and a liquid crystal display, has been widely used because of its numerous advantages such as thin body, energy saving, and no radiation. Most of the liquid crystal display devices available on the current market are backlight-type liquid crystal display devices, which include a liquid crystal panel and a backlight module, with the backlight module as one of the key components of the liquid crystal display device. The backlight module is classed into a side-in backlight module and a direct type backlight module based on the incident position of the light source; wherein for the side-in backlight module, the LED light bar of the light source is arranged at the edge of the backplane behind the liquid crystal panel, and the light emitted from the LED light bar enters a light guide plate through a light-entering face at a side of the light guide plate, then is emitted from a light-outgoing face of the light guide plate after reflection and diffusion, and finally forms a surface light source for the liquid crystal panel via an optical film group. Because the side-in backlight module needs less LEDs than the direct type backlight module, it has many advantages such as a low cost and being conducive to making the liquid crystal display device have a narrow frame and be ultra thin, and is thus being used more and more widely.
However, because the width of the LED light bar of the side-in backlight module needs to keep consistent with the thickness of the light guide plate, the width of its frame cannot be reduced infinitely. The subsidiary structure of the side-in backlight module has to be simplified for further reducing its thickness. As shown in FIG. 1, an existing side-in backlight source is generally composed of an LED 1, a PCB 2 and a heatsink 3, wherein the LED 1, because of the high heat productivity itself, needs to be attached to the heatsink 3 by a thermal conductive adhesive 4 for dissipating heat sufficiently. Because of the presence of the heatsink, it is very limited to reduce the thickness of the frame of the liquid crystal display device in this structure. As shown in FIG. 2, if the heatsink is removed from this backlight source, the entire thickness of the backlight source can be significantly reduced; however, after the thickness is reduced, due to the lack of the heatsink, the heat dissipation of the LED light bar then becomes a very big problem.